* MM-11065: Allow to search and get archived channels from the API
* Fixing more tests
* Add some unit tests
* Add includeDeleted parameter to session permissions check function
* More test fixing
* Adding archive channels list in channels search
* Add restriction for archived channel edition
* Reverting permissions checks modification
* Changed the query parameter to include_deleted
* Enable search archive channels as true by default
* Adding tests for verify search on deleted channels
* Allowing to override archive channels during the imports
* Fixed test
* Search in archive channels from the API must be explicitly requested
* Removing includeDeleted parameter from GetChannelByName and GetChannelByNameForTeam
* Back to ViewArchivedChannels config
* Fixing tests
* Reverting GetChannelByName parameter
* Add include deleted parameter on GetChannel functions in plugins api
* Fixing tests
* clean up plugins GoDoc:
- eliminate plugin.NewBlankContext() as unnecessary
- export ValidIdRegex as a string vs. the less readable var
- add/update various documentation strings
- hide everything by default, except where used by client plugins or the mattermost-server. The exception to this rule are the `*(Args|Returns)` structs which must be public for go-plugin, but are now prefixed with `Z_` with a warning not to use.
- include a top-level example to get plugin authors started
This is not a breaking change for existing plugins compiled against
plugins-v2.
* remove commented out ServeHTTPResponseWriter
* update examples to match developer docs
* add missing plugin/doc.go license header
